egl/wayland: Don't invalidate buffers on no-op resize

The Wayland platform's resize_callback is invoked from libwayland-egl when wl_egl_window_resize() is called. The resize call is the only place for the application to insert dx/dy arguments to wl_surface_attach().

When modifying the cursor hotspot (as in wayland/wayland#148 (closed)), we want to set dx/dy, but leave the surface size the same. If we get wl_egl_window_resize() with the same width and height argument as we already have, we do not need to invalidate our existing drawable.

Signed-off-by: Daniel Stone daniels@collabora.com